1. Field of the Invention
The present invention relates to a color cathode ray tube and a color selection electrode device of a color cathode ray tube for restricting the position which an electron beam reaches.
2. Description of the Prior Art
In a general color cathode ray tube, a panel portion (panel glass) 3 is welded through frit to the open end of a funnel portion 2 having a neck portion 1 so as to constitute a vessel 4, as shown in FIG. 30. A phosphor screen 6 is formed on the inner surface of a face plate 5 of the panel portion 3, and a color selection electrode device 7 is disposed opposite to the phosphor screen 6. Electron beams respectively corresponding to red, green and blue, for example, are landed on the corresponding phosphors after they are regulated by a color selection electrode device 7.
FIG. 31 is a perspective view of a conventional color selection electrode device of a cathode ray tube. In FIG. 31 an opposing pair of longitudinal frame members 10a and 10b are provided and the gaps therebetween are bridged by left and right arm portions 10c and 10d. A multiplicity of filaments which constitute a color selection electrode 11 are stretched between the top end surfaces of the opposing longitudinal frame members 10a, 10b. Several damper wires 12 are provided between the left and right arms 10c and 10d as a damping material in such a manner that the damper wires 12 intersect the filaments 11.
The color selection electrode device 7 is attached to the inside of the panel portion 3 by three- or four-point holding.
In manufacturing the conventional color selection electrode device 7, the pair of arm portions 10c, 10d composed of an elastic material are first welded to the opposing pair of frame members 10a, 10b at the vessel points or in the vicinity thereof. A load is applied to the welding points of the opposing pair of longitudinal frame members or at predetermined points in the vicinity thereof by two-point support so as to shorten the distance between the supporting points by bending the pair of arms 10c, 10d by a predetermined amount within their elastic regions, as shown in FIG. 32. In FIG. 33, the broken lines and the solid lines respectively show the longitudinal frame members 10a, 10b and the arm portions 10c, 10d before and after the load is applied. As shown in FIG. 33, when a load is applied to the longitudinal frame members 10a, 10b in the vicinity of both ends, namely, at the vessel points or two points in the vicinity thereof, each of the longitudinal frame members is bent and the distance therebetween is shortened. In this state, a color selection electrode 11 which is composed of a multiplicity of metal filaments are stretched between the longitudinal frame members 10a, 10b and welded thereto, as shown in FIG. 32. Thereafter, when the load between the supporting points of the longitudinal frame members 10a, 10b is removed, the shortened distance between the longitudinal frame members 10a, 10b is restored to the original distance by the restoring force of the arm portions 10c, 10d each of which is made of an elastic material, and a tension is applied to the stretched color selection electrode 11. Several damper wires 12 are provided between the arm portions 10c, 10d by spot welding in such a manner that the damper wires 12 intersect the color selection electrode 11, as shown in FIG. 31, thereby completing the color selection electrode device 7.
In a conventional color selection electrode device having the above-described structure, since it is important to apply a predetermined tension to the filaments, which constitutes the color selection electrode, in order to prevent the screen from vibrating due to the resonance of the filaments with an external vibration, the frame is disadvantageously required to have a complicated structure, a large size and a great weight. In addition, since the points of each longitudinal frame member at which the load is applied are two points in the vicinity of both ends thereof, it is difficult to obtain a predetermined tension which is uniform at any point in a plane, as shown in the tension distribution in FIG. 34. It is therefore necessary to provide damper wires as a damping material for filaments as the color selection electrode have an insufficient tension, and the shadows of the wires are disadvantageously projected onto the screen, thereby making it difficult to obtain a high-definition picture.